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p-type Cu

Tin monoxide (SnO) is considered as one of the most important p-type oxides available to date. Thin films of SnO have been reported to possess both an indirect bandgap (~ 0.7 eV) and a direct bandgap (~ 2.8 eV) with quite high hole mobility (~ 7 cm 2 /Vs) values. Moreover, the hole density in these films can be tuned from 10 15 –10 19 cm − 3 just by controlling the thin film deposition parameters. Because of the above attributes, SnO thin films offer great potential for fabricating modern electronic and optoelectronic devices. In this article, we are reviewing the most recent developments in this field and also presenting some of our own results on SnO thin films grown by pulsed laser deposition technique. We have also proposed a p–n heterostructure comprising of p-type SnO and n-type ZnO which can pave way for realizing next-generation, all-oxide transparent electronic devices.

Two-dimensional inorganic materials are emerging as a premiere class of materials for fabricating modern electronic devices. The interest in 2D layered transition metal dichalcogenides is especially high. Particularly, 2D MoS2 is being heavily researched due to its novel functionalities and its suitability for a wide range of electronic and optoelectronic applications. In this article, the progress in mono/few layer(s) MoS2 research is reviewed by focusing primarily on the layer dependent evolution of crystal, phonon, and electronic structure. The review includes extensive detail into the methodologies adapted for single or few layer(s) MoS2 growth. Further, the review covers the versatility of 2D MoS2 for a broad range of device applications. Recent advancements in the field of van der Waals heterostructures are also highlighted at the end of the review.

Tin oxide has been demonstrated as an ideal material for fabricating p-type and n-type thin film transistors (TFTs) for transparent CMOS type device fabrication. Both p and n-type conduction was observed in the thin films, prepared from metallic tin target by simply varying the oxygen flow rate during RF magnetron sputter deposition. Films deposited at room temperature were amorphous in nature, which after annealing at 200◦C in air, crystallized to SnO and/or SnO2 phases. The TFTs fabricated on thermally oxidized silicon substrates showed high field effect mobility of 4.13 and 16 cm2/Vs with drain current on-off ratio 6 × 102 and 107 respectively for SnO p-type and SnO2 n-type TFTs. These are the highest values for p-type and n-type oxide TFTs fabricated from same source material. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0091509jss] All rights reserved.

Thin film heterojunctions of p-CuO/n-ZnO are prepared by magnetron sputtering and their electrical properties are investigated without and with external illumination. Radio-frequency (rf) sputtering in reactive oxygen–argon atmosphere is optimized to achieve phase-pure p-CuO thin films with mobilities up to 6.6 cm2 Vs−1 and hole concentrations in the order of 1017 cm−3. Intrinsic ZnO and conducting ZnO:Al are deposited by rf magnetron sputtering to form heterojunctions with CuO in both substrate and superstrate configurations with various Ohmic contacts to p-CuO. Heterojunctions in the substrate configuration do not possess diode properties, while devices in the superstrate configuration show clear rectifying characteristics with a threshold voltage (VTH) of 0.66 V and a forward-to-reverse current ratio of ∼450 at VTH. These junctions exhibit a weak photovoltaic effect under illumination, but reasons for the poor photoresponse are still to be identified.

ZnO:Al nano-polycrystalline thin films were deposited by radio-frequency magnetron sputtering on glass substrates. The analysis of the morphology reveals well-connected whiskers with a preferred c -axis orientation perpendicular to the substrate and a dense columnar grain structure. The as-deposited films exhibited a low electrical resistivity of 1 × 10 − 3 Ω cm. Annealing in air produces an increase of the resistivity by more than three orders of magnitude and an increase in the absolute value of the Seebeck coefficient proportional to the resistivity. Annealing of the as-deposited sample in reducing Ar/H 2 atmosphere leads to a decrease in both the resistivity and the absolute value of the Seebeck coefficient. The change in the electrical transport properties is caused by the absorption and desorption of oxygen. Both resistivity and Seebeck coefficient recover to their initial values during annealing of the air-treated sample in reducing Ar/H 2 atmosphere, indicating a reversible process. The analysis by transmission electron microscopy after annealing reveals a stable columnar grain structure with an increase of the grain size. The increase in grain size is larger when the sample is annealed in reducing rather than in oxidising atmosphere. In summary, the reducing Ar/H 2 atmosphere was found to be advantageous for the thermoelectric properties resulting in a maximum power factor of 0.3 mW/K 2 m at 800 K.

2D materials are considered promising candidates for developing next-generation high-performance energy efficient electronic, optoelectronic, and valley-tronic devices. Though metal oxides are widely used in the fabrication of many advanced devices, very little work has been reported on their properties in 2D limit. This article reports the discovery of a new 2D materials system, 2D tin monoxide (SnO). Layer by layer growth of SnO on sapphire and SiO2 substrates is demonstrated using a pulsed laser deposition method. The number of SnO layers is controlled by controlling the number of laser shots during the deposition process. Raman spectroscopic and X-ray photoelectron spectroscopic analysis confirms the formation of phase pure SnO layers. Field effect transistors (FETs) using few layer SnO channels grown on SiO2 substrates are successfully fabricated. These FETs show typical p-channel conduction with field effect mobility ranging from 0.05 to 1.9 cm2 V−1 s−1. Field effect mobility varies with the number of SnO layers and decreases on either sides of the optimum layer numbers (12), which is explained based on charge screening and interlayer coupling in layered materials.